Effects of muscular response for the intensity of vibratory stimulus applied on the ankle tendon

The present study was conducted to measure the individual threshold value for the somatosensory system of the human body, the thresholds value of vibratory stimulus were assessed through the ascent and descent methods. In the interests of the attainment of this study`s goal, comparing the thresholds value measured and change of state of the muscles when applied on the ankle tendon connected to muscles, changes in threshold measurement accuracy due to the differences in measuring methods were discussed. The experiment was conducted by constructing systems to stimulate somethetic sensibility by vibratory stimulus, ultrasound imaging system and EMG system. Five adult males were involved in this experiment. According to the results of experiments, the threshold value of somatosensory stimulation measured by the ascent method was greater than the threshold values measured by the descent method. And the muscular response to the somatosensory stimulation applied to the tibialis anterior tendon showed a larger rate of change with the ascending stimulus than with the descending stimulus. The results of this study could serve as a basis to discuss the reliability of the measurement method of the human body’s individual threshold value for the somatosensory system through the ascent and descent methods and can be used as reference data for the integration and performance threshold measurement methods

A Two Alternative Forced Choice Method for Assessing Vibrotactile Discrimination Thresholds in The Lower Limb

The development of an easy to implement, quantitative measure to examine vibration perception would be useful for future application in clinical settings. Vibration sense in the lower limb of younger and older adults was examined using the method of constant stimuli (MCS) and the two-alternative forced choice paradigm. The focus of this experiment was to determine an appropriate stimulation site on the lower limb (tendon versus bone) to assess vibration threshold and to determine if the left and right legs have varying thresholds. Discrimination thresholds obtained at two stimulation sites in the left and right lower limbs showed differences in vibration threshold across the two ages groups, but not across sides of the body nor between stimulation sites within each limb. Overall, the MCS can be implemented simply, reliably, and with minimal time. It can also easily be implemented with low-cost technology. Therefore, it could be a good candidate method to assess the presence of specific deep sensitivity deficits in clinical practice, particularly in populations likely to show the onset of sensory deficits

Pairing voluntary movement and muscle-located electrical stimulation increases cortical excitability

Learning new motor skills has been correlated with increased cortical excitability. In this study, different location of electrical stimulation (ES), nerve or muscle, was paired with voluntary movement to investigate if ES paired with voluntary movement a) would increase the excitability of cortical projections to tibialis anterior and b) if stimulation location mattered. Cortical excitability changes were quantified using motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation at varying intensities during four conditions. Twelve healthy subjects performed 50 dorsiflexions at the ankle during nerve or muscle ES at motor threshold. ES alone was delivered 50 times and the movement was performed 50 times. A significant increase in the excitability from pre- to post-intervention (P=0.0061) and pre- to 30 minutes post-intervention (P=0.017) measurements was observed when voluntary movement was paired with muscle ES located at tibialis anterior. An increase of 50±57% and 28±54% in the maximum MEPs was obtained for voluntary movement paired with muscle-located and nerve-located ES, respectively. The maximum MEPs for voluntary movement alone and muscle-located ES alone were -5±28% and 2±42%, respectively. Pairing voluntary movement with muscle-located ES increases excitability of corticospinal projections of tibialis anterior in healthy participants. This finding suggests that active participation during muscle-located ES protocols increases cortical excitability to a greater extent than stimulation alone. The next stage of this research is to investigate the effect in people with stroke. The results may have implications for motor recovery in patients with motor impairments following neurological injury

CEREBRAL SOMATOSENSORY POTENTIALS EVOKED BY MUSCLE STRETCH, CUTANEOUS TAPS AND ELECTRICAL STIMULATION OF PERIPHERAL NERVES IN THE LOWER LIMBS IN MAN

Somatosensory cerebral evoked potentials were recorded in man to natural forms of somatosensory stimulation of the lower extremity including stretching of the muscle tendons, tapping on muscle bellies and tapping on cutaneous surfaces. These potentials were compared with those evoked by electrical stimulation of peripheral nerves measuring the amplitudes and latencies of the evoked potential components and defining the effects of stimulus variables on these parameters. Spinal cord potentials could only be detected to electrical stimuli. Mechanical stimulation of tendons and muscle bellies evoked scalp potentials at latencies earlier than those evoked by electrical stimulation of the peripheral nerve and by cutaneous stimulation at the same level of the leg. Muscle receptors, most probably muscle spindles, are the source of the short latency components obtained by the stretching of tendons and tapping on muscle bellies. The proximal location of these receptors as well as very rapid spinal conduction account for the latency difference. The potentials were larger to electrical stimulation of nerve trunks than to mechanical stimulation of tendons or skin, suggesting the asynchronous activation of a smaller number of fibres by the latter. Individuals with the largest potentials to one form of stimulation usually had the largest potentials to the other modes of stimulation. The use of physiological stimuli such as muscle stretch to test the transmission in specific neural pathways might be useful in investigating the processing of relatively selective afferent volleys using noninvasive evoked potential recordings

Firing properties of muscle spindles supplying the intrinsic muscles of the foot in unloaded and free-standing humans

Human posture and locomotion are dependent on the sensory apparatus – involving muscle spindles, cutaneous afferents and the vestibular system – that provides proprioception. In my previous work with my Bachelor of Medical Research, I investigated the relationship between galvanic vestibular stimulation and the sensitivity of muscle spindles of the long muscles of the leg. While that study showed no correlation between these systems it was limited by the lack of subject postural threat. In order to record from muscle spindles directly during unsupported free-standing, a new methodology for microneurographic recording from the posterior tibial nerve at the ankle was developed. For the first time, we have been able to identify the firing properties of muscle spindle endings in the small (intrinsic) muscles of the foot, as well as mechanoreceptors in the skin of the sole, while the participant is standing unsupported. This thesis presents this methodology along with the recordings made. In Study 1, the firing properties of 26 muscle spindles supplying the intrinsic muscles of the foot are described in unloaded conditions. Their responsiveness to stretch and related joint movements is shown to be similar to those in the short muscles in the hand and the long leg muscles. Only 27% were spontaneously active, of which there was no consistent resting firing rate or discharge variability. In Study 2, activity from 12 muscle spindles supplying the intrinsic foot muscles in unsupported free-standing conditions is described. In this group 50% were spontaneously firing and 67% had activity correlated with changes of centre of pressure recorded by a force plate, primarily (88%) along the anteroposterior axis. In Study 3, the activity of 28 multiunit cutaneous afferent recordings, as well as of 15 single-unit cutaneous afferents, supplying the sole of the foot in unsupported free standing is described. Activity of cutaneous afferents was found to be dependent on receptor type and location of receptive field. The data presented in this report is proof of this novel methodology’s suitability for detailed study into the sensory sources in the foot contributing to maintaining the upright posture

Excitatory postsynaptic potentials in rat neocortical neurons in vitro. III. Effects of a quinoxalinedione non-NMDA receptor antagonist

1. Intracellular microelectrodes were used to obtain recordings from neurons in layer II/III of rat frontal cortex. A bipolar electrode positioned in layer IV of the neocortex was used to evoke postsynaptic potentials. Graded series of stimulation were employed to selectively activate different classes of postsynaptic responses. The sensitivity of postsynaptic potentials and iontophoretically applied neurotransmitters to the non-N-methyl-D-asparate (NMDA) antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) was examined. 2. As reported previously, low-intensity electrical stimulation of cortical layer IV evoked short-latency early excitatory postsynaptic potentials (eEPSPs) in layer II/III neurons. CNQX reversibly antagonized eEPSPs in a dose-dependent manner. Stimulation at intensities just subthreshold for activation of inhibitory postsynaptic potentials (IPSPs) produced long-latency (10 to 40-ms) EPSPs (late EPSPs or 1EPSPs). CNQX was effective in blocking 1EPSPs. 3. With the use of stimulus intensities at or just below threshold for evoking an action potential, complex synaptic potentials consisting of EPSP-IPSP sequences were observed. Both early, Cl(-)-dependent and late, K(+)-dependent IPSPs were reduced by CNQX. This effect was reversible on washing. This disinhibition could lead to enhanced excitability in the presence of CNQX. 4. Iontophoretic application of quisqualate produced a membrane depolarization with superimposed action potentials, whereas NMDA depolarized the membrane potential and evoked bursts of action potentials. At concentrations up to 5 microM, CNQX selectively antagonized quisqualate responses. NMDA responses were reduced by 10 microM CNQX. D-Serine (0.5-2 mM), an agonist at the glycine regulatory site on the NMDA receptor, reversed the CNQX depression of NMDA responses

The Effect of Astym Treatment on Muscle Performance

Purpose: Astym treatment is a manual therapy intervention that stimulates tissue regeneration and treats pain, limited mobility, and muscle weakness associated with musculoskeletal pathology. The purpose of this study was to determine if Astym treatment administered to the lower extremity would result in an immediate change of maximal force output during a unilateral isometric squat test among individuals with a lower extremity injury. Methods: Forty-five subjects (14males; 31females) aged between 18-65 years participated in this study. The subjects were randomized into 3 treatment groups: 1) Control group - received no treatment 2) Placebo group - received a sham Astym treatment 3) Astym treatment group- received Astym treatment to the lower extremity. After familiarization to the operations of a computerized leg press machine, a baseline measure of maximal force output (pre-test) was determined by the average of 3 trials with a 30 second rest period between the trials. The subjects then received the designated treatment intervention. Immediately following the treatment intervention the subjects were retested (post-test) using identical testing procedures by an investigator who was blinded to the treatment intervention received by the subjects. The percent change of maximal force output from pre-test to post-test measures was compared using a one-way analysis of variance with alpha set at 0.05. A Tukey\u27s post-hoc analysis determined the statistical differences between the groups. Results: The treatment intervention had a significant effect on the percent change of maximal force output [F(2,42) = 7.91, p = 0.001]. Tukey\u27s post hoc analysis demonstrated that the percent change of maximal force output was significantly greater in the Astym group (15+18%change) compared to the placebo (-6+11%change) and control (-1+17%change) groups. No significant difference (p=0.68) was noted between the control and placebo groups. Conclusions: Astym treatment to the involved lower extremity increased maximum force output during an isometric squat test immediately following treatment. The results of this study suggest that Astym treatment can be used as an intervention for the immediate improvement of muscle performance for patients presenting with muscular weakness caused by a lower extremity musculoskeletal injury

Effects of sensory information over the motor and somatosensory cortex activity during standing

The purpose of this study was to identify changes in cortical hemodynamics of motor and somatosensory cortex related to balancing tasks during inhibition of muscle spindles and cutaneous receptors of the dominant leg. Data were obtained from twelve participants (age: 24.8 +/- 4.59 years). The study consisted of four randomized order visits to identify cortical hemodynamic changes while standing under normal conditions (Ctrl), with muscle spindles inhibited (MSI), with cutaneous receptors inhibited (CB), and with the muscle spindles and cutaneous receptors inhibited (BOTH). Muscle spindles were inhibited by applying five minutes of vibration over the soleus muscle; pre- and post-vibration (MSI and BOTH) H-reflex amplitude was measured for later statistical analysis. Lidocaine was applied and left over the foot sole for 30 minutes; sensitivity threshold and two-point discrimination variables were obtained under normal conditions (Ctrl) and anesthetic effect (CB and BOTH). Cortical hemodynamics were measured using an fNIRS placed over each participant's head while performing two counterbalanced blocks of bipedal and unipedal standing with the eyes closed. During MSI and BOTH five minutes of vibration were applied before each block of standing tasks. Statistical analysis consisted of performing different repeated measures ANOVA; then, if needed, post-hoc test consisted of several paired samples t-test (corrected for multiple comparisons). Findings revealed that, compared to pre-, H-reflex amplitude was significantly lower after vibration. Lidocaine findings were inconclusive with a higher sensitivity threshold on the heel during BOTH than Ctrl, but two-point discrimination did not show any significant effect among the visits. Body sway was not different among visits but increased from bipedal to unipedal standing. Cortical hemodynamics revealed that mean oxyhemoglobin activity was not different during bipedal standing among the visits, but it was different during visits that inhibited muscle spindles compared to visits that did not inhibit muscle spindles. In conclusion, muscle spindle inhibition of the soleus muscle can alter the motor and somatosensory cortex's cortical hemodynamics during unipedal standing, but these changes did not influence balance performance. Cutaneous block might not be achieved by applying lidocaine over the foot sole for 30 minutes; therefore, conclusions regarding the cutaneous receptors' influence were not possible

A study on the effect of vibration stimulation of the sub-perception threshold intensity on lower leg muscle based on the SEPs

This paper aims to study the effect of vibration stimulation of the sub-perception threshold on the tibialis anterior muscle and triceps surae muscle based on the somatosensory evoked potentials (SEPs). EEG is measured by applying the vibration stimulation to tibialis anterior tendon and Achilles tendon, and the sub-perception threshold intensity is selected through SEPs analysis. For this purpose, EEC collection and analysis system was used. In addition, analyzing changes in muscle strength and muscle reaction time by applying the selected sub-perception threshold intensity to tibialis anterior tendon and Achilles tendon. For this, maximum voluntary contraction (MVC), and muscle reaction time (MRT) are analyzed by using the EMG collection and analysis system. Vibration stimulation of the sub-perception threshold intensity analysis results, muscle strength is increased, muscle reaction time decreased